1. Technical Field
The present invention relates generally to a multicasting system and method for a vehicular communication network and, more particularly, to a multicasting system and method for a vehicular communication network, which are capable of improving the reliability of the transmission of TDMA-based data packets between a roadside communication device and a vehicular communication device.
2. Description of the Related Art
Multicasting has the advantage of reducing traffic because it transfers the same frame to a plurality of target terminals at the same time. Thanks to this advantage, multicasting is utilized in a variety of applications. In particular, many applications requiring vehicular communication have high needs for multicasting and broadcasting.
The current IEEE 802.11p standard does not support the retransmission of multicast and broadcast frames. For example, in the case of unicast transmission, a reception is acknowledged via a reception ACK frame, and a source terminal retransmits the same frame if the ACK frame is not received.
In this case, fair throughput is achieved in connection with other neighboring terminals by exponentially increasing a contention window, and the source terminal adjusts a physical layer rate based on the frame error rate. However, a multicast service does not support a protocol which is used in the above-described unicast transmission, and therefore it is difficult to provide Quality of Service (QoS).
Although technologies for solving the problem have been proposed, most of them are related to multicast techniques based on the CSMA/CA-based MAC technology. That is, the TDMA-based MAC technology may be suitable for vehicle control and driving context-aware applications that require high-reliability communication within a predetermined communication delay time. Although the CSMA/CA-based MAC technology has high fairness, it has the problem of being unable to guarantee the success of communication within a predetermined delay time when network traffic increases.